Prevalence and new phenotypic and radiologic findings in congenital onychodysplasia of the index finger.

Congenital onychodysplasia of the index finger (COIF) is a rare condition characterized by dysplastic changes in the nail with variable phenotypic manifestations. Its prevalence is unknown. We describe three newborn patients with various clinical and radiologic expressions of this entity. The first, born to a mother treated with multiple antidepressant drugs, had bilateral nail dysplasia of the index finger without bony involvement. The second presented with bilateral hypoplastic nail of the index finger and bilateral symphalangism of the fifth finger; aplastic distal phalanges of the second finger was also noted radiologically. The third baby (born to a diabetic mother treated with insulin), had micronychia and brachydactyly of the right index finger and syndactyly of the second and third fingers; the radiologic finding was bilateral brachymesophalangia of the index finger. It would seem that, besides the nail dysplasia of the index finger, COIF may also be associated with bone dysplasia of the same finger.